Mihai Marasteanu

1
Summary of Shingles Work at the University of
Minnesota

• Mihai Marasteanu Adam Zofka

2
Introduction

• Two smaller projects
• Missouri samples
• Mixture testing
• Minnesota samples
• Mixture and binder testing

3
Missouri Specimens
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Creep Stiffness Results, PG 58-28
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Creep Stiffness Results, PG 64-22
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Strength Results, PG 58-28
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Strength Results, PG 64-22
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Conclusions Missouri Specimens

• For PG-22 mixture, at temperatures below -10C,
  the addition of shingles increases the mixture
  stiffness considerably
• Most likely results in increased thermal cracking
  and fatigue cracking occurrence
• Also in PG-28 mixtures but to a much lesser
  extent
• Strength properties were not significantly
  affected by the addition of shingles for both the
  PG-22 and PG-28 mixtures.

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Conclusions Missouri Specimens

• Worth mentioning that during the cutting process,
  the saw shutoff automatically due to the intense
  heat generated when cutting the specimens
  prepared with shingles. This did not occur for
  the specimens prepared only with RAP.

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Minnesota Specimens

• Three types of materials
• 20 reclaimed asphalt pavement (RAP),
• 15 RAP 5 Tear-off recycled asphalt shingles
  (RAS),
• 15 RAP 5 Manufactured RAS.
• All three mixtures contain the same virgin
  asphalt binder PG 58-28
• Binders were chemically extracted (MnDOT) and
  tested (MnDOT UMN)

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Asphalt Mixture Creep Stiffness
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Asphalt Mixture Strength
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Missouri vs. Minnesota
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Conclusions Minnesota Mix Specimens

• Addition of tear-off RAS material increases
  significantly the stiffness of the mixtures at
  all test temperatures
• Largest increase at -20C
• Addition of manufactured RAS material increased
  stiffness only at 0C and -10C
• Stiffness at -20C reached the lowest observed
  value from all tested materials
• Strength properties were not significantly
  affected by the addition of shingles

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Conclusions Minnesota Mix Specimens

• Results indicate lower stiffness values for the
  Minnesota RAP mixtures compared to Missouri
  mixtures
• Similar observation for the combinations of RAP
  RAS
• Suggests differences in the tear-off RAS
  materials used in the two studies

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Minnesota Specimens Extracted Binders

• Bending Beam Rheometer (BBR) tests were performed
  on the binders extracted
• Direct Tension Tests (DTT) were performed at
  temperatures around the temperature at which
  S(60s) 300MPa

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Minnesota Specimens Extracted Binders
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BBR Results

• Addition of shingles changes the properties
• Lowers the stiffness!!!
• Lowers the m-values
• Changes the relaxation properties
• Need to look at master curve
• Need to look at thermal stresses

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BBR Master Curves
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BBR Master Curves All Materials
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Thermal Stresses
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Direct Tension Results
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Critical Temperature
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Critical Temperature
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Critical Temperature
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Conclusions - Binder Results

• The two types of shingles perform differently
• The manufactured material seems to be beneficial
• Decreases stiffness
• Does not affect strength
• Reduces critical temperature very little
• The tear off affects properties in a negative way
  (although it also decreases stiffness)
• Lowers strength significantly
• Increases critical temperature

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Conclusions - Binder Results

• The role of m-value not fully understood
• Spec requires higher m-values (gt 0.300)
• However, authors showed that lower m-values
  result in less thermal stress accumulation
• Needs to be further investigated
• The limited data also shows that binder and
  mixture results do not always agree
• Most likely due to other parameters from mixture
  preparation (gradation, air voids, etc)

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Thank you!